1. Field of the Invention
The present invention relates to a wheel alignment adjusting device for adjusting alignment of wheels of a vehicle.
2. Description of the Related Art
Generally, wheels of a vehicle are provided with a camber angle for ensuring traveling stability of the vehicle, and are provided with a toe angle for preventing irregular wear caused by the provision of the camber angle.
Or, conversely, a toe angle is provided in order to balance the forces generated at the front tires and at the rear tires of the vehicle so as to ensure travelling stability of the vehicle, and the toe angle and the camber angle are combined so as to carry out adjustment for improving the traveling stability of the vehicle and minimizing the irregular wear of the tire under limiting conditions such as the structural dimensions of the vehicle and the like.
Accordingly, in order to improve the traveling stability and irregular wear resistance of the tire when the vehicle is traveling, it is important to adjust the toe angle and the camber angle, which are positional angles (wheel angles) applied to each wheel.
Adjustment of the toe angle and the camber angle is carried out with the vehicle disposed on a wheel alignment adjusting device.
The wheel alignment adjustment device includes a loading stand upon which a vehicle is loaded.
Loading portions are provided on the loading stand in correspondence with the tires. A wheel is loaded on each loading portion.
The loading portion includes a wheel rotating device such as a roller for rotating the wheel or an endless track, and force sensors which can sense the amounts of forces and the directions (vehicle longitudinal direction and vehicle transverse direction) of forces received by the wheel which is being rotated. On the basis of the results of sensing, the amounts of change of the toe angle and the camber angle and the like are displayed on a display device at the wheel alignment adjusting device.
Because tread bases of vehicles differ in accordance with the type of vehicle, the wheel alignment adjusting device includes a function of changing the distance, in the vehicle transverse direction, between the loading portions.
In a conventional wheel alignment adjusting device, the loading portions at the vehicle transverse direction right side (xe2x80x9cright side loading portionsxe2x80x9d) and the loading portions at the vehicle transverse direction left side (xe2x80x9cleft side loading portionsxe2x80x9d) are supported so as to be movable along the vehicle transverse direction with respect to the loading stand. The right side loading portions and the left side loading portions are moved independent of one another by driving devices such as cylinders or the like, and are moved the same distances to the left and the right with respect to the transverse direction center of the device. (Namely, the right side loading portions and the left side loading portions are moved in directions of approaching each other in the vehicle transverse direction or in directions of moving away from each other in the vehicle transverse direction.) Thus, at least two driving devices for moving the loading portions, i.e., at least two for the left side and at least two for the right side, are needed, making the structure complex.
Further, it is difficult to accurately position the loading portions at the left and right sides (i.e., to fix the loading portions with respect to the loading stand). When the loading portions are moved, due to play of the device for example, the amount of change in the distance between the two loading portions for the front wheels, and the amount of change in the distance between the two loading portions for the rear wheels change. (There is actually the need to make the amount of change in the distance between the two loading portions for the front wheels and the amount of change in the distance between the two loading portions for the rear wheels equal). Further, the orientation of the wheel and the orientation of the loading portion (the direction in which the wheel is rotated) differ for each wheel, which may affect the accuracy of detection.
The present invention was developed in order to overcome the above problems, and an object of the present invention is to provide a wheel alignment adjusting device in which loading portions, upon which wheels of a vehicle are loaded, can be positioned with high accuracy.
A first aspect of the present invention is a wheel alignment adjusting device having a loading stand provided with a plurality of loading portions on which wheels of a vehicle are loaded, wherein loading portions at one vehicle transverse direction side are fixed to the loading stand, and loading portions at another vehicle transverse direction side are supported so as to be movable along a vehicle transverse direction with respect to the loading stand.
The vehicle is loaded on the loading stand such that the wheels of the vehicle are disposed on the corresponding loading portions.
When the vehicle transverse direction distance between the loading portions is changed in accordance with the tread base of the vehicle, the loading portions at another vehicle transverse direction side (e.g., the right side) are moved with respect to the fixed loading portions of one vehicle transverse direction side (e.g., the left side).
The loading portions at both vehicle transverse direction sides are not moved. Rather, the loading portions only at the other vehicle transverse direction side are moved. Thus, the number of driving devices for moving the loading portions can be decreased, which simplifies the structure of the wheel alignment adjusting device. Further, when the loading portions are moved, the loading portions can be positioned very accurately.
A second aspect of the present invention is a modified wheel alignment adjusting device of the first aspect, wherein the loading portions at another vehicle transverse direction side are mounted to a sub-base which is supported so as to be movable along the vehicle transverse direction with respect to the loading stand.
The other vehicle transverse direction side loading portions (for the front wheel and the rear wheel) are mounted to the sub-base, and the sub-base is structured so as to move along the vehicle transverse direction with respect to the loading stand. Thus, as compared with a case which loading portions for the front wheels and loading portions for the rear wheels are respectively moved independently, the accuracy of positioning the other vehicle transverse direction side loading portions (for the front wheel and the rear wheel) is improved.
In a third aspect of the present invention, the wheel alignment adjusting device of the second aspect further comprises a fixing device for fixing the sub-base and the loading stand.
Because the sub-base can be fixed to the loading stand by the fixing device, the sub-base can be prevented from coming out of position due to an external force or the like.
A fourth aspect of the present invention is a modified wheel alignment adjusting device of the third aspect, wherein the fixing device is provided at each of vehicle longitudinal direction sides of the sub-base.
The fixing device is provided at each of the vehicle longitudinal direction sides of the sub-base. Both vehicle longitudinal direction sides of the sub-base are fixed to the loading stand by the fixing devices. Thus, the positional accuracy of the sub-base is improved over a case in which the sub-base is fixed at one place.